Two-part acrylic adhesive is advantageous in that it can be cured at room temperature, can adhere in a large area, is quickly cured and exhibit adhesiveness to various plastics, and thus it is used in the field such as automobile, building, marine, wind power, etc.
However, the two-part acrylic adhesive is disadvantageous in that the adhesive strength is lower than that of the one-part epoxy adhesive and the elongation is lower than that of the urethane adhesive. Consequently, its usage is limited in fields of application requiring stronger adhesive strength such as structural adhesives for vehicles, and high elongation such as adhesion outside the vehicle.
There is also a trade-off relationship between flexibility/toughness and strength in various adhesive compositions. Usually, in order to increase flexibility and toughness in the adhesive composition, a rubbery polymer is added, but the addition of such a rubbery polymer tends to adversely affect the modulus and ultimately the strength of the adhesive. Therefore, there is a demand for development of an adhesive composition exhibiting excellent adhesiveness without sacrificing strength.